An energy storage system, such as a flow battery, may include one or more cells that operate to store energy provided from a source, and to discharge energy to a device to do work. Each cell may have a cathode, an anode and a separator disposed between the cathode and anode for separating chambers of the cell that receive electrolyte. The separator may permit ionic flow between the cathode and anode to facilitate energy storage in the system, as well as discharge of energy from the system. Each cell may further include one or more flow screens that are each positioned between one of the electrodes and the separator, and that are configured to influence flow of electrolyte.